Expert Witness Journal Issue 67 June/July 2026 - Flipbook - Page 78
maintenance and inspection requirements. The
failure to identify the defect allowed foreseeable
user interaction to result in harm.
In practice, claims frequently focus on the immediate
as though it were the cause. Whilst this initially looks
convincing, this approach is increasingly vulnerable
to forensic and legal scrutiny.
Case study– entanglement during
ship birthing
Consider the above scenario of a user reaching
into a machine and sustaining injury. Labelling
the cause as “user error may describe the 昀椀nal
action, but it does not explain why the hazardous
underlying cause remained accessible. The critical
forensic question is not what the individual did, but
why the system of use permitted injury to occur, the
root cause.
Incident Summary
The injured party was attaching lines to a newly
installed capstan alone when a tangle began to
develop. While the capstan remained in operation,
an attempt was made to adjust the lines. During this
interaction, the 昀椀ngers became caught in the line,
resulting in a crushing injury.
Equipment does not fail randomly
Conclusion
From an engineering standpoint, for the use of
equipment, workplace safe systems of work are
designed on the premise that:
•
•
•
The injury occurred because the system permitted
foreseeable user interaction with moving lines.
The actions of the injured party constituted the
immediate cause. The underlying causes were the
absence of supervision and the lack of engineered
measures to prevent access during operation. The
failure to recognise the training needs of newly
installed equipment and implement an engineered
safe system of work was the root cause.
People make mistakes
People take shortcuts
People deviate from training from time to time.
These assumptions are fundamental to established
safety‑engineering principles, including:
•
•
•
•
Hierarchies of guarding and protection
Fail‑safe design philosophies
Interlocks and system redundancy
Ergonomic control layout and people–machine
interface design
Regulatory and legal context
The Health and Safety Executive has consistently
emphasised that employers must anticipate
foreseeable user interaction and misuse, and that
training alone cannot compensate for unsafe design
or systems of work. The risk should be eliminated
through adequate engineering measures included
in the safe system of work.
When an injury occurs, it is often because the system
has tolerated foreseeable human behaviour without
adequate engineering mitigation. In such cases,
the presence of user action does not negate system
failure, rather, it highlights a design or control
de昀椀ciency that allowed predictable behaviour to
result in harm.
Case study – electric saw injury
during operations
Incident Summary
Unsafe use of saw machinery, speci昀椀cally a failure
to keep hands clear of the blade. The activity
being undertaken formed part of normal, routine
production operations. The physical guarding
system in place was intended to provide primary
protection against contact with the blade. However,
damage and degradation of the guard reduced its
e昀昀ectiveness as a protective measure. As a result, the
system relied on operator vigilance to compensate
for diminished safeguarding performance.
Conclusion
The injured party’s interaction with the saw was
the immediate cause of the incident, rather than
its root cause. The underlying cause was that the
safeguarding system was not delivering its intended
level of protection. The root cause of the injury was
systematic failures to implement statutory equipment
EXPERT WITNESS JOURNAL
76
JUNE 2026
